Titti Postiglione, head of the department's emergency office, said more snow could fall from peaks in the Gran Sasso mountain range in the central Abruzzo region because the temperature was rising, while further quakes were possible.

"This is an enormously complex rescue operation," she said.

The gabled peaks of parts of the roof and a row of windows were the only sections of the four-storey Hotel Rigopiano visible after the wall of snow smashed into the four-star spa resort on Wednesday evening.

"This is a tragedy of enormous proportions," said Health Minister Beatrice Lorenzin.

Local authorities said about 30 people had been in the building at the time, including two children. The only survivors found were two men who had been outside when the disaster struck.

"The hotel is almost completely destroyed. We've called out but we've heard no replies, no voices," said Antonio Crocetta, a member of the Alpine Rescue squad.

"We're digging and looking for people," he told Reuters by phone from the isolated location.

Rescue workers entered what appeared to be a lobby decorated with oil paintings and plants, where a landslide had torn through a wall, television footage showed.

Mattresses and furniture were spotted dozens of metres away and sniffer dogs were helping with the search.

"I am alive because I went to get something from my car," Giampiero Parete told medical staff. Italian media said he had been on holiday with his wife and two children, who are missing.

Prime Minister Paolo Gentiloni called for national unity, saying Italy was caught in an "unprecedented vice" of earthquakes and heavy snows.

The rescue operation was hampered by deep snow which has fallen on the Gran Sasso in recent days. Drifts made snow as deep as five metres in some places and snow ploughs struggled to cut a path up winding mountain roads.

The first rescuers arrived at 4.30 am after having to ski through a blizzard to reach the site. After dawn broke, emergency services sent in helicopters.

A base camp for rescue workers was set up in the town of Penne, some 10 km away, where ambulances waited.

The avalanche shunted the 43-room hotel, which is 1200 metres above sea level, about 10 metres down the hill, according to media reports.

Italian media said guests at the hotel had checked out and were waiting for a snow plough to arrive to open up the road and let them down the mountain when the avalanche struck.